What are some possible causes of headaches that NEVER go away no matter how much fluid i drink, sleep i *try* to get, eat right and take pills for??

I spoke to my GP about it on several occassions but each time he has said its due to stress and me not relaxing as much as i can to sleep.

Ive had scans before (like yearrrs ago) and nothing showed up.

Im over taking medications that never help. My body is so used to Panadol, Nurofen, Panadeine Forte, Panadeine extra strong, Advil.....its beyond a joke now